I also feel sorry for you and your family for having to go through this.
Having worked alongside drug councilors i have seen many families and individuals go through similar. However, to blame a plant is not really helpful for yourselves or your son, and whoever told you that was the reason is not really helping either, sorry.
My advice to educate was aimed purely at your attitude and comments and your sons situation, not at you as a person or your experiences, so i stand by my advice and its up to you wether you accept help or take it personally.
Anyway, like above, my thoughts are with you and hopefully the future will brighten for you and your family, dont give up hope.